Of course you would not want an important conversation be cut in the middle just because the telephone battery ran out.
Today, there are already telephone batteries replacements that are available even in Amazon. It is important to remember to always buy those with the best manufacturer specs and not the refurbished.
Quality should always be the primary factor in buying electronic gadgets and devices. It pays. It would be a waste to buy cheaper ones with poor quality. Of course, you already know that.